Incomplete combustion in internal combustion engines may cause visible smoke exiting the exhaust system. This may contravene emission regulations and may also be perceived as negative by users and other members of the public with regards to health and environment issues.
A multi-cylinder internal combustion engine can produce excessive smoke during low engine speeds if the air feed passage terminates at the manifold. Combustion airflow fed into the manifold from a feed passage can have an unstructured characteristic and can become chaotic once in the manifold. The chaotic airflow motion in the manifold continues into the inlet port to the combustion chamber and causes the in-cylinder swirl motion to become unstable resulting in incomplete combustion. Smoke issues are limited at higher speeds due to the airflow structure changing with the airflow speed. One solution is to adapt the port shape design, but this will result in high development costs and may have a negative impact on the performance at higher engine speeds where emission levels are critical. Further challenges may arise due to restrictions to the design of the manifold itself, as the availability of multiple customer options may depend on particular manifold configurations. The present disclosure is directed at overcoming one or more of the above identified problems.